John V (John Palaeologus)pālˌēŏlˈəgəs, 1332–91, Byzantine emperor (1341–91), son and successor of Andronicus III. Forced to fight John VI (John Cantacuzene), who usurped the throne during his minority, he came into power in 1354. In his reign the Ottoman Turks took Adrianople and Philippolis, conquered Serbia, and exacted tribute from the emperor. John vainly tried to heal the schism between East and West in order to secure Western aid against the Turks. He professed (1369) the Roman Catholic faith at Rome; while returning to Constantinople he was briefly imprisoned for debt in Venice. In 1371 he recognized the suzerainty of the Ottoman sultan Murad I. Deposed (1376) by his son Andronicus IV, he was restored in 1379. In 1390 his grandson, John VII, briefly usurped the throne. John V was succeeded by his son Manuel II.